1. Field of the Invention
The present invention relates to a lumbar support device built in the seat back of an automotive seat, and is particularly directed to an improved lumbar support device permitting its easy installation in the seat back.
2. Description of the Prior Art
As disclosed in the Japanese Laid-Open Patent Publication No. 55-49, a conventional lumbar support device of this kind is constructed such that a torsion spring having a lumbar plate secured thereto is pivotally and rotatably mounted on a pin or the like. This pin is secured at a bracket fixed on a back frame, and therefore, to effect this pivotal mounting of the torsion spring involves winding one end part of the torsion spring around the pin and fixing the thus-prepared pin to the bracket of the back frame by use of a great number of various tools and machines. This results in a quite poor or slow operation of the seat assembly. What is worse, the structure of such a device is rather complicated, so that many steps of assembling processes are required for producing the device.